1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the present invention relates to devices and methods for disrupting, collecting, and removing occlusive material from blood vessels and other body lumens.
Thrombosis and atherosclerosis are common ailments which occur in humans and which result from the deposition of thrombus and clot on the walls of blood vessels. When hardened, such deposits are commonly referred to as plaque. Such deposits are most common in the peripheral blood vessels that feed the limbs of the human body and the coronary arteries which feed the heart. Stasis, incompetent valves, and trauma in the venous circulation cause thrombosis, particularly occurring as a deep vein thrombosis in the peripheral vasculature. When such deposits build-up in localized regions of the blood vessel, they can restrict blood flow and cause a serious health risk.
In addition to forming in the natural vasculature, thrombosis is a serious problem in “artificial” blood vessels, particularly in peripheral femoral-popliteal and coronary bypass grafts and dialysis access grafts and fistulas. The creation of such artificial blood vessels requires anastomotic attachment at at least one, and usually at at least two, locations in the vasculature. Such sites of an anastomotic attachment are particularly susceptible to thrombus formation due to narrowing caused by intimal hyperplasia, and thrombus formation at these sites is a frequent cause of failure of the implanted graft or fistula. The arterio-venous grafts and fistulas which are used for dialysis access are significantly compromised by thrombosis at the sites of anastomotic attachment and elsewhere. Thrombosis often occurs to such an extent that the graft needs to be replaced within a few years or, in the worst cases, a few months.
A variety of methods have been developed for treating thrombosis and atherosclerosis in the coronary and peripheral vasculature as well as in implanted grafts and fistulas. Such techniques include surgical procedures, such as coronary artery bypass grafting, and minimally invasive procedures, such as angioplasty, atherectomy, transmyocardial revasculaturization, and the like. Of particular interest of the present invention, a variety of techniques generally described as “thrombectomy” have been developed. Thrombectomy generally refers to procedures for the removal of relatively soft thrombus and clot from the vasculature. Removal is usually achieved by mechanically disrupting the clot, optionally with the introduction of thrombolytic agents. The disrupted thrombus or clot is then withdrawn through a catheter, typically with a vacuum or mechanical transport device.
Thrombectomy generally differs from angioplasty and atherectomy in the type of occlusive material which is being treated and in the desire to avoid damage to the blood vessel wall. The material removed in most thrombectomy procedures is relatively soft, such as the clot formed in deep vein thrombosis, and is usually not hardened plaque of the type treated by angioplasty in the coronary vasculature. Moreover, it is usually an objective of thrombectomy procedures to have minimum or no deleterious interaction with the blood vessel wall. Ideally, the clot will be disrupted and pulled away from the blood vessel wall with no harmful effect on the wall itself.
While successful thrombectomy procedures have been achieved, most have required comprise between complete removal of the thrombosis and minimum injury to the blood vessel wall. While more aggressive thrombectomy procedures employing rotating blades can be very effective at thrombus removal, they present a significant risk of injury to the blood vessel wall. Alternatively, those which rely primarily on vacuum extraction together with minimum disruption of the thrombus, often fail to achieve sufficient thrombus removal.
For these reasons, it would be desirable to provide improved apparatus, systems, methods, and kits for performing thrombectomy procedures. It is particularly desirable that the present invention provide thrombectomy procedures which are both capable of effective thrombus and clot removal while minimizing the risk of injury to the blood vessel wall. The methods and procedures of the present invention should be suitable for treatment of both arteries and veins within the peripheral, coronary, and cerebral vasculature. Even more particularly, the present invention should provide for the treatment of native and synthetic grafts which are subject to thrombosis and clotting, such as arterio-venous grafts and fistulas, bypass grafts, and the like. In addition to treatment of the vasculature, the methods, systems, devices, and kits of the present invention should also be useful for treating other body lumens which are subject to occlusion and blockage due to the presence of occlusive materials within the lumen. At least some of these objectives will be met by the inventions described hereinafter.
2. Description of the Background Art
U.S. Pat. No. 5,904,698, describes a catheter having an expansible mesh with a blade or electrode for shearing obstructive material which penetrates the mesh when the mesh is expanded in a blood vessel. Other catheters having expansible meshes, cages, and/or shearing elements are described in U.S. Pat. Nos. 5,972,019; 5,954,737; 5,795,322; 5,766,191; 5,556,408; 5,501,408; 5,330,484; 5,116,352; and 5,410,093; and WO 96/01591. Catheters with helical blades and/or Archimedes screws for disrupting and/or transporting clot and thrombus are described in U.S. Pat. Nos. 5,947,985; 5,695,501; 5,681,335; 5,569,277; 5,569,275; 5,334,211; and 5,226,909. Catheters having expansible filters at their distal ends are described in U.S. Pat. No. 4,926,858 and PCT publications WO 99/44542 and WO 99/44510. Other catheters of interest for performing thrombectomy and other procedures are described in U.S. Pat. Nos. 5,928,186; 5,695,507; 5,423,799; 5,419,774; 4,762,130; 4,646,736; and 4,621,636. Techniques for performing thrombectomy are described in Sharafudin and Hicks (1997) JVIR 8: 911-921 and Schmitz-Rode and Günthar (1991) Radiology 180: 135-137.